I’ve been getting the message in Safari for about the last month or so. Maybe after the upgrade to MacOS 10.14.5
I mailed Jim Robinson about this when it happened to me.
He responded, Make sure to use the SECURE LINK to log in every time.
That link is https://www.freerepublic.com
You can paste & bookmark it if you dont want to type it in every time.
www.freerepublic.com or freerepublic.com are not secure links, and can allow others to access your account.